The invention relates to power-driven conveyors and, more particularly, to modular conveyor belts constructed of rows of belt modules hingedly interlinked end-to-end by hinge pins.
Conventional modular conveyor belts and chains are made up of modular links, or belt modules, arranged in rows. Spaced apart link ends extending from each end of the modules include aligned apertures. The link ends along one end of a row of modules are interleaved with the link ends of an adjacent row. A pivot rod, or hinge pin, journalled in the aligned apertures of the end-to-end-connected rows, connects adjacent rows together to form an endless conveyor belt capable of articulating about a drive sprocket.
In many industrial applications, articles are allowed to accumulate on a continuously moving conveyor belt before being off-loaded. Friction between the conveying surface of the moving belt and the accumulated articles causes the articles to push against each other increasing backline pressure. Backline pressure can cause damage to the articles, excessively load the conveyor belt and its drive components, and accelerate belt wear. Rotatable elements, such as rollers, in rolling contact with the undersides of conveyed articles have been used to reduce friction and lower backline pressure.
In other conveyor applications, articles must be pushed off the side of a constantly moving or stop-and-go conveyor belt. Rollers oriented with their axes of rotation in the direction of belt travel have been used to provide low friction rolling contact with the undersides of conveyed articles being pushed off the side of a conveyor.
Arscott U.S. Pat. No. 4,231,469, issued Nov. 4, 1980, discloses a conveyor comprising a plurality of interconnected cradles and a rotatable member mounted in each cradle. The rotatable members extend above the respective cradle for rolling contact with an object placed on the conveyor to allow the objects to move relative to the conveyor. The Arscott patent discloses rotatable members with axes of rotation in the direction of belt travel for side off-loading and perpendicular to the direction of belt travel for low backline pressure.
One shortcoming of the Arscott conveyor and other roller-top belts is that they are difficult to clean owing to the many surfaces and nooks and crannies associated with the rollers. Cleanability is especially important in some industries, such as meat-handling, where bacteria can form in and spread from difficult-to-clean areas.
Another shortcoming of many low backline pressure conveyors is the placement of a roller on the pivot rod. Such a placement requires fewer or thinner link ends resulting in less belt pull strength or narrow rollers resulting in high contact pressure on conveyed articles. Thus, there is a need for a modular conveyor belt that features low backline pressure or low-friction side transfer and that is easy to clean.